Autoclave curing gas silicate block. What is better non-autoclaved or autoclaved aerated concrete? How to improve properties

Aerated concrete happens autoclave and non-autoclave, and many builders are wondering - what are the differences between them.

Let's figure it out together, but looking ahead, let's say that autoclaved aerated concrete is a much better material, and below we will tell you why.

What is autoclaved aerated concrete?

Autoclave treatment - stage of processing aerated concrete with high temperature (190 ° C) under high pressure during 12 hours... Autoclaves are metal containers in which cut gas blocks are placed.

Autoclaving is done for the following purposes:

1. acceleration of aerated concrete hardening;
2. increased strength;
3. reduction of shrinkage;
4. improving the uniformity of the structure;
5. improved block geometry.

The autoclave also changes the structure of aerated concrete at the molecular level, forming new material – tobermorite... This synthesized stone has properties that cannot be obtained in normal conditions at standard pressure and temperature.

Let us repeat that non-autoclaved aerated concrete hardens in natural conditions, and for its production it is expensive and modern equipment not required. In other words, many manufacturers stamp gas blocks in their garages, which does not inspire much confidence.

Now let's take a closer look at the differences in aerated concrete, and we'll start with strength.

Comparison of autoclaved and non-autoclaved aerated concrete

It is important to note that in the video non-autoclaved aerated concrete is tested, to which fiber has been added, it significantly increases the strength of the blocks. But note that in reality, fiber in the production of non-autoclaved aerated concrete is not used by everyone, since it is quite expensive.

Strength

Aerated concrete without an autoclave is less durable, especially when fresh. After all, it, like ordinary concrete, needs more time to gain strength, while autoclaved concrete has accelerated hardening hundreds of times due to high-temperature steam treatment. But even with the complete hardening of both materials, the strength of the autoclave is higher by half or more.

For example, autoclaved aerated concrete grades D500 and D600 have strength classes B2.5 - B3.5, while a non-autoclaved analogue of the same brand is gaining B2 class at best.

Shrinkage

Large shrinkage of blocks can create multiple cracks in the masonry; moreover, cracks can appear within a year or more. To minimize such processes, block shrinkage should be minimal.

Shrinkage of non-autoclaved aerated concrete is from 3 to 5 mm per meter, autoclaved - ten times less. That is, autoclaved aerated concrete practically does not give shrinkage cracks, with proper laying.

Block geometry

The geometry of the blocks is also very important, and the smoother the blocks are, the better. Indeed, if the blocks differ from each other by 5 mm, then the difference in level must be leveled with glue, and these are cold bridges, which greatly impair the thermal insulation characteristics of the masonry.

Moreover, thick seams tend to shrink heavily, which again can cause cracks. Experienced builders will say that the difference in levels can be leveled with a grater on aerated concrete, but imagine how long it will take.

Now let's think about where the geometry of the blocks will be better, on high-tech factory equipment with autoclaves, or in a garage? The answer is obvious!

Most builders believe that the best, smoothest blocks come from AEROC. The average price per cube of their aerated concrete is 4000r.

Uniform structure

Uniformity means the number of voids (bubbles) that are distributed in a certain way in aerated concrete, and the more uniform they are, the better. The autoclaved aerated concrete technology guarantees an ideal distribution of voids, due to the fact that bubbles are formed and immediately harden, and individual blocks are obtained after cutting one large block.

Non-autoclaved aerated concrete is made in a completely different way. Foam and blowing agents are added to the concrete mixture. As a result, bubbles can rise closer to the surface, and heavier elements fall down. As a result, the distribution of bubbles will be uneven.

Now let's think about what it threatens. Firstly, where there are fewer bubbles, there is less strength, and where there are few bubbles, there is a cold bridge through which heat will escape faster. That is, the strength and thermal conductivity indicators of non-autoclave aerated concrete are very unstable.

Thermal conductivity

Smoothly moving from the topic of structure uniformity to thermal conductivity, let us say that the uneven bubble structure worsens the average thermal conductivity of the block, and it is natural that the uniformity of the bubbles in autoclaved aerated concrete is better and, therefore, the thermal insulation is also better.

Output

Autoclave and non-autoclave aerated concrete are very different from each other in a number of parameters, and it is safe to say that autoclave material surpasses its counterpart in all respects, except for one - price. Yes, non-autoclave gas blocks cheaper, but if you count how many problems arise when laying it, how many additional materials, work and time will have to be done, we advise you to think carefully when making your choice.

It is better to build a house competently once, from quality material, and be sure that it will stand for many years without problems.

Currently, the demand for building blocksmade from aerated concrete and you can often hear the question: "What is the difference between autoclaved and non-autoclaved aerated concrete?" Within the framework of this article, we will discuss the main differences and performance of these products.

Material characteristics

First you need to clarify the terminology. Cellular concretes are understood as all lightweight concretes during the manufacture of which cells (pores) are formed in the structure. In turn, it is divided into aerated concrete and aerated concrete, depending on the technology for creating pores. The next stage of division arises depending on the hardening process - autoclave or non-autoclave.

Autoclaving

When steaming the mixture necessary for the production of aerated concrete at a pressure above 12 atmospheric and a temperature above 190 degrees Celsius in devices called autoclaves, a new material is obtained with characteristics that cannot be obtained under normal conditions - this process is called autoclaving. As a result, the structure of concrete changes at the molecular level and a new material with completely unique characteristics is obtained, called tobermorite.

Non-autoclaved concrete is cured naturally or with steam, but under normal atmospheric pressure solution with pores, while autoclaved aerated concrete is an artificial stone. They are fundamentally different in many respects. They have a different composition and different physical and technical parameters, which are an order of magnitude higher for autoclaved aerated concrete.

Main characteristics of materials:

Quality

The quality of autoclaved aerated concrete is always, without a doubt, since its production is extremely difficult and impracticable in artisanal conditions technological process... During production, it is necessary to simultaneously control many processes and parameters, for this on modern factories the degree of automation reaches 95 percent and practically excludes the possibility of non-compliance with the technology through human fault. Manufacturing usually takes place in large factories and the material is brought to the construction site already in the form of finished building blocks. The technology is described in the modern GOST of 2007 and must be confirmed by test reports and product certificates. For the manufacture of foam blocks and aerated concrete, such capacities are not required and at first glance it seems like a plus. After all, the products are cheaper. But can you eliminate the risk of low-quality production or even handicraft production? When buying autoclaved aerated concrete, this question will not arise, because you can always be 100% sure of its quality.

Uniformity

Non-autoclaved aerated concrete is produced by adding a gas generator to the concrete mass and mixing it. As a result, there are cases in which the bubbles, having less weight, float up, and the fillers, on the contrary, settle down. As a result, finished products in the form of building blocks are heterogeneous and may even have different parameters. In the case of the production of autoclaved aerated concrete, everything is completely different. The process of gas formation and hardening occurs simultaneously and proceeds uniformly throughout the volume of the material produced. As a result, the pores in the finished material are evenly distributed and after the completion of the stage of cutting the finished material into building blocks, they are obtained with an ideal quality and a homogeneous structure.

Mountings

Since aerated concrete is very strong, it is possible to fix heavy materials and equipment on it. For example, ventilated facades made not only of light materials, but also heavy ones of porcelain stoneware. In order for the fastening to be reliable, anchor bolts with polyamide expandable elements are used. As a result, when using, for example, a 10x100 anchor, the axial pull-out load of up to 700 kg is maintained, which is very close to the values \u200b\u200bof a solid brick.

Shrinkage

When gaining strength, significant shrinkage of non-autoclaved aerated concrete occurs as a result of which cracks appear in the finished masonry, plaster falls off or the finishing layer peels off. All this lasts for 3-5 years until the material reaches its strength. Often, when using such materials, it is impossible to just putty and paint the walls, as a rule, more complex work is required. Inside, you have to finish with plasterboard, and outside use bricks or curtain walls. Such problems do not arise when using autoclaved aerated concrete, since it gains its strength even during the production process. For comparison, the shrinkage index of autoclaved aerated concrete is 0.5 mm / m, but non-autoclaved from 1 to 3 mm / m.

Manufacturing precision

In the production process for non-autoclaved materials, they rely on indicators of permissible values \u200b\u200bfrom the old GOST, as a result, the finished building blocks have a large difference in geometric characteristics. For autoclaved aerated concrete blocks, such problems do not exist, since all production is carried out according to modern GOST and the discrepancies in the parameters of the finished product are minimal. Due to the large error in geometric dimensions, a number of problems arise when using non-autoclaved aerated concrete:

• Increases required amount solution and, as a result, the cost of construction.
• Cold bridges are formed due to thick seams.
• Leveling the surface of the walls becomes a rather laborious process.

Thermal insulation

The thermal insulation level of both materials is very good. But you can consider this issue from the side of the efficiency of use different materials and costs to achieve the same effect. The level of thermal insulation, among others, is influenced by such an indicator as the density of the material. The higher the density level, the lower the thermal insulation values \u200b\u200bof the building blocks will be. For example, to use the material as a constructive one, and even more so for load-bearing walls, high strength is required. To achieve the required performance using non-autoclaved aerated concrete, a density of at least 700 kg / m3 is required. This means that for high-quality thermal insulation, the wall thickness should be about 65 cm.Under the same conditions, to achieve the desired level of strength, autoclaved aerated concrete with a density of 500 kg / m3 can be used and the wall thickness will already be about 40 cm.

Outcome

At first glance, when building houses, it seems obvious that the price advantage is not in favor of autoclaved aerated concrete. But in the end, taking into account all the shortcomings of non-autoclave materials and the amount required to eliminate them, this plus comes to naught. Autoclaved aerated concrete is superior to non-autoclaved aerated concrete in almost all respects.

Autoclaved aerated concrete is a type of porous concrete processed in a special way. Manufacturing technology provides such positive traits, as lightness, high vapor permeability, dimensional accuracy and excellent thermal insulation. The scope of application is practically not limited by the climatic features of the regions and the size of the structure: it is used both in private construction and in industrial construction. But when choosing, it is important to take into account some of the requirements for masonry and subsequent finishing, due to fragility and hygroscopicity.

The blocks are made from concrete, aggregate and water. A required component is a foaming agent - aluminum powder. When it reacts with lime, it forms many bubbles, distributed throughout the mass. The size of the cavities varies from 1 to 3 mm, they communicate with each other, but are closed. Finished elements - solid cement mixconsisting of pores on ⅔. This makes the material very lightweight and significantly reduces the cost of raw materials. Weight depending on density - from 300 to 700 kg / m3.

The composition of autoclaved and non-autoclaved aerated concrete is identical:

• quartz sand crushed by the wet method or washed natural fine fraction - 30-40%;
• portland cement M400, M500 - from 15 to 50%;
• lime - 12-26%;
• aluminum powder or paste as a blowing agent - 0.1-1%;
• chemical additives that regulate foaming and hardening rate (caustic soda, sodium sulfate, calcium chloride) - 0.05-0.45%;
• water - 45-70% of the total weight of all dry components.

Each manufacturer selects its own recipe and ratio of components, often fillers are replaced with industrial waste and aerated concrete.

Production technology

Autoclave blocks are manufactured in accordance with GOST 31360-2007.

• In a ball mill, sand is mixed with water and crushed to produce sand slurry.
• The sand with all other components is placed in an airtight container.
• A homogeneous mixture with an introduced gas generator is poured into large molds up to half the volume.
• After the completion of foaming, they are sent for preliminary hardening.
• Solid large blocks are cut into standard elements, a ridge and a groove are formed.
• Placed in a special installation - an autoclave. In it, they are treated with hot steam and high pressure.

It is the production process of autoclave that differs from non-autoclave aerated concrete. The latter is immediately poured into molds of the desired size and dries naturally, therefore it has large differences from the standard dimensions, less clear angles and is inferior in strength. Its production does not require the purchase of an expensive autoclave; therefore, such a product is less expensive.

Autoclaving removes the remaining moisture and changes the characteristics of the material particles. They are converted into an artificial mineral - tobermorite. Products obtained in this way are much stronger, withstand more freezing cycles and have an increased service life. The block is in the autoclave chamber for at least 10 hours.

Advantages and disadvantages of aerated concrete

Autoclave elements have improved performance, but the whole group is united by a large number of advantages over other types of products for the construction of walls, ceilings and partitions:

1. The dimensions are standardized, the maximum geometry deviation does not exceed 2-3 mm - this allows you to make a thin seam, devoid of cold bridges.
2. Aerated concrete is easy to process, cut and drill.
3. Not included harmful substances... The aluminum content is minimal, moreover, it is in a bound state, therefore the material is recognized as environmentally friendly. Even exposure to open flames does not lead to the release of toxic fumes.
4. Complete fire safety. The blocks not only do not burn, but are also able to withstand prolonged exposure to high temperatures without destruction.
5. The breathable structure creates a favorable microclimate in the room with optimal humidity.
6. Not subject to any biological effects and decay.

Aerated concrete building can have thin walls and still be warmer than standard brickwork... This reduces heating costs by 25-30%. Sound insulating properties are several times better in comparison with concrete, wood and brick.

The light weight of the blocks provides savings in foundation arrangement. It also allows large elements to be made while lifting for one person. Construction is going many times faster and without the use of special equipment.

The main disadvantage is hygroscopicity, but it is easy to eliminate it: it is enough to cover the walls under finishing immediately after the completion of the work. Care is required, since the products are fragile and capable of splitting from impact. There are strict restrictions on the number of storeys for elements of different densities and requirements for strengthening window and doorways... Autoclaved aerated concrete has a high cost in comparison with non-autoclaved.

Scope of application

By changing the number and size of pores (density) and the ratio of the main components, manufacturers obtain blocks of different properties:

1. Thermal insulation with density up to 400 kg / m3. It is worth purchasing for the construction of small buildings or wall insulation from other materials.
2. Structural and thermal insulation - 500 kg / m3. They can be bought for a private or low-rise building.
3. Structural, the most dense - 700 kg / m3. Suitable for load-bearing walls, but with limited load. The structure should be no higher than 3 floors.

Autoclaved aerated concrete is used mainly in private construction for the construction of cottages, country houses, garages, outbuildings. But it is also suitable for load-bearing walls of low-rise buildings, as well as for masonry in frame structures without restrictions on the number of storeys. It is successfully used to create insulated attics.

Autoclaved aerated concrete is an artificial material that has proven itself in the construction of industrial and residential buildings. It is a kind of aerated concrete. Since the material is becoming more and more popular in the construction of private buildings, you should know what its characteristics are, what autoclaving is, the differences between autoclaved concrete and non-autoclaved concrete, their pros and cons.

Figure 1. Autoclaved aerated concrete

Autoclaving provides accelerated hardening of concrete. The difference between building materials and analogues is their higher strength.

Autoclaving is a steaming process under conditions high temperature environment and high pressure. It takes place in special metal capsules. When the finished blocks are loaded into the autoclave, the pressure is 0.8-1.3 MPa, and the temperature rises to 175 0 -191 0 С. It takes approximately 12 hours for complete hardening.

Autoclaved aerated concrete undergoes changes at the molecular level. As a result of processing, a new mineral, tobermorite, is formed. It has unique properties. The main feature, what distinguishes autoclaved concrete from non-autoclaved concrete, is that the first is an artificially obtained stone, and the second is a frozen sand-cement mortar.

Autoclaved aerated concrete blocks have special characteristics: composition, operational characteristics, physical and technical parameters. Autoclaved and non-autoclaved concrete are different in most parameters.

Features of autoclaved aerated concrete masonry

When erecting buildings from material produced using an autoclave for aerated concrete, you need to know a few general rules masonry and have an idea of \u200b\u200bthe features of working with aerated concrete blocks:

• To begin with, the tubs always choose the most protruding corner. This will be the place with the minimum layer thickness.
• The first row is laid using a cement-sand mortar.
• Then aerated concrete blocks distribute to the rest of the corners. When performing masonry, they act as landmarks. A cord is pulled between them.
• In cases where the length of the wall exceeds 10 meters, several additional ones are installed between the corner landmark blocks.
• The initial row is laid out completely. If gaps arise during operation, the blocks are cut using an electric saw or hacksaw to the required size.

• After a short break (2-3 hours), the first row is reinforced.
• When laying the remaining rows, mainly glue is used. It is applied with a trowel and leveled with a comb. The seams are offset by 20%.
• Since the glue sets quickly, it is recommended to level the aerated concrete blocks as soon as possible. It is almost impossible to correct shortcomings.

Pros and cons of materials

Autoclaved blocks have a number of advantages in comparison with non-autoclaved concrete:

• Strength. On the walls lined with autoclaved aerated concrete, it is allowed to mount shelves, cabinets, as well as objects that have a large mass. For example, air conditioners. Aerated concrete that has not been autoclaved will not withstand such loads.
• High quality. Since autoclaved aerated concrete can be produced only in industrial conditions, in terms of quality, it compares favorably with non-autoclave counterparts, which are often produced by handicraft methods.
• Less shrinkage during operation. The amount of shrinkage directly depends on the strength of the building material. The average indicator for autoclaved aerated concrete is 0.5 mm / m, for non-autoclaved aerated concrete - up to 3 mm / m.

The pros and cons of autoclaved aerated concrete are presented in the table:

Advantages	disadvantages
Strength.	Absorption of moisture, which, at low temperatures, destroys the structure of autoclaved aerated concrete.
Environmental friendliness, safety for the environment.	Problems with fixing fasteners, the need to use specialized products for aerated concrete.
Refractoriness.	Fragility, which is often revealed already at the stage of transportation.
Easy to cut and grind.
Vapor permeability for a comfortable microclimate.
Thermal conductivity, which ensures heat retention in buildings.
Frost resistance, allowing to withstand up to 150 cycles of freezing and thawing.
Mold and rot resistant.

Overview of the main qualities of the material

Figure 2. Autoclaved aerated concrete

Taking into account the advantages and disadvantages of autoclaved aerated concrete blocks, the main properties can be distinguished:

• Strength. Autoclaved aerated concrete has the following characteristics: density up to 800 kg / m 3, compressive strength class B2.5-B3.5.
• Stability of quality, which is regulated by GOST, adopted in 2007. Products manufactured in industrial plants are accompanied by quality certificates.
• Uniformity of the material. Its difference lies in the fact that in the course of production the processes of gas formation and hardening occur simultaneously in the entire volume of raw materials. The finished aerated concrete blocks have pores of the same size, there are no air bags in them.
• Environmentally friendly, breathable. In buildings made of autoclaved aerated concrete blocks, a microclimate is maintained that is similar to that of a wooden frame. In the production, mineral raw materials are used that are resistant to mold, mildew, and decay.
• Shrinkage. Aerated concrete blocks do not undergo shrinkage deformations, since they gain sufficient strength during production and processing in an autoclave.
• Accuracy of geometric dimensions. This indicator is determined by GOST. Deviations should not exceed 2 mm in width, 3 mm in length and 1 mm in thickness. In the production of aerated concrete building materials, they resort to cutting large masses. This allows you to maintain the required block sizes with high precision, which ultimately improves the quality of the masonry.

Aerated concrete production technology

The technological process includes the following stages:

• Combining water and sand with particle size reduction.
• Introduction of lime, cement and table salt. Mixing of raw materials.
• Pouring the resulting solution into the formwork.
• Hydrogen reaction with gas evolution, which creates a porous structure.
• Solidification of the mass within 2-3 hours.
• Block cutting with industrial strings.
• Autoclaving of aerated concrete.

Areas of use

The scope of application of autoclaved aerated concrete is not limited to the construction of industrial buildings. The material is used for the construction of residential buildings.

The blocks are suitable for single or double layer exterior walls. Partitions for fire-prevention rooms are made of them.

Other areas of use:

• construction of floor slabs in buildings;
• production of wall panels for industrial and residential buildings.

The demand for autoclaved aerated concrete is so high that the producers of this material have united in a national association, which is called upon to discuss the prospects for the development of the industry and develop new requirements for quality and innovative approaches to the organization of production.

4.5 / 5 ( 2 voices)

Aerated concrete is classified as aerated concrete and is a uniformly closed pore of air, equally distributed over the material. Aerated concrete blocks are an ecological and high quality product. They are produced in exact dimensions and have the correct shape, are easy to process and are ideal for finishing.

Aerated concrete is distinguished by the type of binder and type of hardening. Product processed at high pressure and the temperature in a specialized oven - an autoclave, has a name - autoclaved aerated concrete. It has many positive characteristics, and the use of this material improves the quality of construction, and, importantly, significantly reduces the cost of construction.

Such aerated concrete is made from crushed quartz sand, gypsum, cement, lime (quicklime), andrigide and water. At the exit, autoclaved aerated concrete is 2/3 filled with air pores. Proportions of aerated concrete solution for an autoclave furnace according to the standard:

• cement - 20%;
• quartz sand - 60%;
• quicklime - maximum 20%;
• aluminum residues - no more than 1%.

The process of making autoclaved aerated concrete

It is made using the following technology:

• Combine sand and water and grind into sandy sludge.
• The resulting mass is poured into a mold for a chemical reaction between an alkali solution and highly dispersed aluminum. This process promotes hydrogen formation to create bubbles.
• Hydrogen bubbles foam the solution and create a porous structure. It is at this stage that the concrete is distributed into forms and left to ripen and harden for 2-3 hours.
• The hardened material is cut with industrial strings into blocks of a given size.
• The blanks are sent to the final stage - for steaming in an autoclave, where the blocks are processed in temperature conditions 180-200 degrees under pressure for 12 hours. An autoclave apparatus is a sealed chamber where a product is processed that requires heating at a pressure higher than atmospheric pressure.

Autoclaving removes excess moisture from the product, completing the hardening process, after which aerated concrete gains its final properties.

Advantages of porous autoclaved concrete

The uniqueness of this material lies in:

• low thermal conductivity;
• increased refractoriness, it is able to maintain combustion for up to 7 hours or more;
• breathability due to increased air permeability;
• mechanical strength;
• lightness due to low density;
• immunity to pest attack;
• resistance to decay and moisture;
• ensuring the correct microclimate in any season.

Gas blocks are capable of holding combustion for up to 7 hours or more

The fact that autoclaved aerated concrete blocks combine the main qualities of wood and brick makes it a unique product. And if we take into account the high frost resistance of the material (it can withstand up to hundreds of frost-defrost), it will become clear that this construction material can be used regardless of the regional climate, without exception.

It is also worth noting the flexible indicators of such a block. Its malleability allows you to create structures of various shapes, embodying various architectural ideas.

The scope of application for the autoclave unit is very wide: the construction of cottages, low-rise buildings and high-rise buildings, industrial and commercial construction, reconstruction work, construction of foundations. Autoclaved aerated concrete does not require a large set of tools to work. Quite enough:

• notched trowel (for working with mortar);
• coarse-toothed hacksaw (for non-standard sawing);
• coarse sandpaper (for leveling);
• rubberized mallet (for stacking blocks);
• containers for the solution (any convenient, a bucket is also possible).

Features of autoclaved aerated concrete

Aerated concrete is special for its low weight. Due to this, the production allows to produce increased sizes, namely: length - 62.5 cm, height - 20 (up to 25) cm, width - 10 (up to 40) cm. Aerated concrete is a very light material. Its lightness and increased size make it simpler to build and speed up the process several times. It facilitates installation so much that not only a specialist, but also an ordinary consumer can handle it.

The advantage of gas blocks is perfectly flat corners and flatness

Almost all batches in the production of such products provide the same unit size. The maximum error is from 1.5 to 3 mm for any direction. Such forms overestimate the angular and edge norms for release. It turns out the clarity of geometric proportions due to the autoclave furnace. It is in it that surfaces acquire smoothness, and corners - clarity.

It is recommended to use an adhesive solution for laying concrete bricks. Such a layer will not only be a more economical option, but also ensure the solidity of the building. This means that it will preserve and increase its thermal insulation performance. If you choose a solution, add some of the glue to it, and also make the mixture more soft. This will help to avoid cold bridging at the seam.